These threads offer a few suggestions for you:
Good luck, Rose.
Hi Rose! I recently wrote a post that I think might help you: http://askannamoseley.com/2012/07/how-to-clean-marble/
Rose here is another thread that may help as well.
The very first thing you should do if these are new floors is to see what the manufactor recommends. Because if you use the wrong product you could void your warrenty. I have a high end cleaning business before I touch anything brand new I go to their manufactors and get cleaning instructions. Saying that I use a neutral cleaner, stone soap, or a squirt of mild dish soap. I use a micro fiber mop. These are amazing but a very soft cloth can work. If you use to much cleaner it will build up so less is better. I squeeze out the mop as much as I can a damp mop. Then you dry the heck out of it. Drying is key to everything. The micro fiber mops can also be used to dry if you have more than one. I am not trying to sell anything but having the right tools is most of the battle. I almost always use a neutral cleaner, or stone soap. Never use vinegar, ammonia or lemon these will etch and And dull the finish.
Go to the marble institute and follow their recommendations.
I forgot to add rinse your floors this is the mosy important step after you wash them and then dry...
And be sure to read the whole comment..above